Throat plate for sewing machine



April 9, 1958 B. HOWARD 3,376,839

i THROT PLATE FOR SEWING MACHINE v Filed May 31, '196e INVENTOR.

BERNARD HOWARD ATTORNEYS United States Patent O 3,376,839 THROAT PLATE FOR SEWING MACHINE Bernard Howard, New Haven, Conn., assigner to Mite Corporation, New Haven, Conn., a corporation of Delaware Filed May 31, 1966, Ser. No. 553,914 9 Claims. (Cl. i12-260) This invention relates to sewing machines, .and more particularly to a substitute throat plate for use wi-th certain sewing machine attachments.

Some attachments provide their own fabric feed, and it therefore becomes necessary to disable the regular feed dogs of the sewing machine. This is usually and most `simply done by removing the slotted throat plate thr-ough which the feed dogs operate, and substituting a throat plate which covers or masks the feed dogs, thereby making them inoperative. This has been done, for example, when using the .attachment disclosed in my copending application Ser. No. 482,466, tiled Aug. 25, 1965, and entitled, Sewing Machine for Making Monograms and Other Designs.

The needle passes downward through a small slot which is dimensioned to lallow f-or zig-zag motion. In practice some difficulty may .arise because of .a tendency of some fabrics to be pushed downward into the slot, and to s-tick in the slot when the needle rises. The primary object of the present invention is t-o overcome this difficulty.

Considered in different aspect, a general object of the invention is to provide an improved throat plate for masking the feed dogs of a sewing machine. A more specific object is to provide .a throat plate for use With the monogrammer disclosed in the aforesaid copending application Ser. No. 482,466.

To .accomplish the foregoing general objects, and other mo-re specific objects which will hereinafter appear, my invention resides in the throat plate elements and their relation one to another, `and to the parts of -a sewing machine, as are hereinafter more particularly described in the following specification. The specification is accompanied by drawings in which:

FIG. 1 is a perspective View showing a monogrammer attachment with the improved throat plate therebeneatn;

FIG. 2 is ya plan vie-w showing the relation ofthe attachment t-o the `sewing machine and throat plate;

FIG. 3 is a plan view of a throat plate embodying features of the present invention;

I FIG. 4 is a vertical -section taken approximately on the vline 4 4 of FIG. 3; and

FIG. 5 is la fragmentary vertical section taken -approxif mately on the line 5-5 of FIG. 3.

Referring to the drawing, and more particularly to FIG. l, the sewing machine attachment there illustrated is the monogram-mer disclosed in -my aforesaid application Ser. No. 482,466. Tlhe attachment 12 is secured to the sewing machine by means of an adapter mounted on the lower end of the usual upright pressure bar 16. The mechanism is actuated by a vfork arm 18 which straddles the clamp screw of the needle bar o-f the sewing machine, which is no-t shown. The fabric is held and moved by a foot which is ia relatively large open fra-me 20, this being carried and moved by the'forward ends 22 and 24 of a slide 23 located at the bottom of the attachment.

The bifur-cated forward end of the slide 23 is given both lateral and longitudinal movements, frequently referred to as X and Y movements respectively, by means of a pattern cam. Tlhe cam is an elongated at bar 26 which is fed through .the attachment from left to right as the sewing operation proceeds. A manually operable knob 28 may be used to preliminarily feed the cam 26 when first inserting it in the attachment. Another knob 30 varies Pce the range of zig-zag width or 'bight, the proportional variation being provided automatically by means of a third cam track on the cam bar 26.

Referring now to FIG. 2 of the drawing, a sewing machine is schematically `repre-sented by a base 32 carrying a head 34 with the usual overhanging arm 36. The miachine .is driven by a motor indicated at 38. The attachment is shown at 12 with a pattern cam 26 which has already been fed nearly all .the way through the attachment. The c-am 26 is disposed yat an angle such that its path of movement clear-s the sewing machine head 34 and the motor 38, regardless of the length of the pattern cam 26.

The new throat plate is indicated at 40 in FIGS. l and 2. It is of large larea in order t-o accommodate the rel-atively large rectangular foot 20 of the attachment, and to allow for the X and Y movement of the foot.

Referring now to FIGS. 3, 4 and 5 of the drawing, the throat plate 4l) has parts 42 disposed over and resting on the sewing machine feed dogs, these being indicated by dotted lines at 44. The parts 42 are arranged t0 rise and fall with the feed dogs 44, the said parts having a s-m-ooth bottom surface at 46 (FIG. 4) on which the feed dogs readily slide, and having .a smooth top surface over which the fabric readily moves. In preferred form the parts 42 are flexible leaf springs which are substantially longer than the feed dogs 44. The mid-portions of the springs are adapted to rise and fall with the feed dogs, and the raised position of the springs is higher than the top surface of the throat plate 40, as is indicated in FIGS. 4 and 5 by lthe broken line posi-tion 42'.

The ends 48 of the springs extend beneath the top of the throat plate, .and the springs normally seek their down position, but they yield resiliently upward when the feed dogs rise.

In the particular case here shown there is a wear strip 50 secured beneath each spring 42, and this wear strip rests on'and receives the sliding motion of the feed dogs. The smooth surface 46 previously referred to is the bottom surface of the wear strip 50. The wear strips are made of hard metal or are case hardened, particularly at the bottom. As will be seen in the drawing, the vertical dimension of the wear strip is such as to produce the desired elevation of the leaf spring about the surface of the throat plate when the feed dog is raised. The Wear strip Si) may be secured to the spring 42 in any desired fashion, including for example, the use of a suitable adhesive. Alternatively, a part of the spring may be indented downward to form an integral wear strip.

The small slot 52 (FIG. 3) receives the needle of the sewing machine. The slot is somewhat elongated sideward to allow for zig-zag motion in the case of a zig-zag sewing machine. It will be evident that the lift of the springs 42 at each side of the slot 52 insures lift of the fabric out ofthe slot.

Considering the present throat plate in greater detail, it conveniently comprises a lower base 54 which has the dimension and outline of the regular throat plate, in order to be received in the opening for the regular throat plate. This base 54 has slots 56 (FIGS. 4 and 5) for the feed dogs, and another slot for the needle. The top plate 40 is of much greater area, and it is disposed directly over and is mounted on the smaller base plate 54. The parts 40 and 54 may be secured together in any desired manner, as by spot welding, or by the use of small screws. The top plate 40 has long slots 58 (FIG. 4) for the leaf springs 42. The ends of the springs are offset downward beyond the ends of the slots 58, and the bottom of the plate 40 may be recessed upward as shown at 60 (FIG. 4), to receive the ends 48. The mounting of the springs 42 between the base plate 54 and the top plate 40 helps secure the springs in position. With this construction there is no need to secure the ends 48 of the spring to the plate 40, and instead they remain free for a slight longitudinal movement accompanying the upward flexing of the spring.

In addition, the wear strips 50 are preferably dimensioned to be received in the relatively short slots 56 of the base plate 54, as is best shown in FIG. 4. This further anchors the springs 42 against longitudinal movement, while freely permitting the desired vertical or pulsating movement caused by the feed dogs 44.

The center slot 61 shown in FIG. 3 receives a third feed dog, but this feed dog is also disabled because of the height of the top of the throat plate. It will be understood that the dimension and shape of the base 54, and the number and location and dimension of the slots 56 and 61, will depend on the particular sewing machine for which the attachment and substitute throat plate are designed.

The large side slots shown at 62 are to provide access to small release pins here suggested at 64, which pins happen to he used in this sewing machine to hold the throat plate in position. In some other sewing machines the throat plate is held by one or more small screws which are readily released, and in such case the present substitute throat plate is similarly provided with holes for screws for the same lpurpose. Instead of the slots 62, there would be openings affording access to the mounting screws.

In the particular case shown the monogram area is two inches square. The foot 20 is considerably larger, and moves an inch either side of center position in X and Y position. The plate 40 is six inches by five and a half inches to accommodate this.

It is believed that the construction and method of use of my improved throat plate, as well as the advantages thereof, will be apparent from the foregoing detailed description. It is useful with any attachment requiring disabling of the feed dogs. It may be used with a buttonholer or with a ruffler, although its most important use is for a monogramrner attachment as here described.

It will be understood that while I have shown and described the invention in a preferred form, changes may be made without departing from the scope of the invention, as sought to be defined in the following claims.

I claim:

1. A throat plate for use in a sewing machine when using an attachment providing its own feed and which therefore requires disabling of the regular feed dogs of the sewing machine, said throat plate comprising means disposed entirely over and resting on the sewing machine feed dogs which means are arranged to rise and fall with the feed dogs while the remaining portions of said throat plate remain fixed, said means having a smooth bottom surface along which the feed dogs readily slide, and having a smooth top surface over which the fabric readily moves.

2. A throat plate as defined in claim 1 in which the said movable means are flexible leaf springs which are substantially longer than the feed dogs, the mid-portions of said springs being adapted to rise and fall with the feed dogs, and the raised position of the springs being higher than the top surface of the throat plate.

3. A throat plate as defined in claim 2 in which the ends of the springs extend beneath the top of the throat plate, and in which said springs normally seek their down position but yield resiliently upward when the feed dogs rise.

4. A throat plate as defined in claim 2, in which there is secured beneath each leaf spring a wear strip which rests on and receives the sliding motion of the feed dog, the vertical dimension of said wear strip -being such as to produce the desired elevation of the leaf spring above the top surface of the throat plate when the feed dog is raised.

5. A throat plate as defined in claim 2, in which there is a lower base having the dimension and outline of the regular throat plate in order to be received in the opening for the regular throat plate, and having slots for the feed dogs and for the needle, and a top plate of much greater area disposed directly over and mounted on the aforesaid smaller base, said top plate having long slots for the leaf springs, the ends of said springs ybeing offset downward at the ends of the slots, and portions of said springs being located between the base plate and the top plate.

6. A throat plate as defined in claim 3, in which there is a lower base having the dimension and outline of the regular throat plate in order to be received in the opening for the regular throat plate, and having slots for the feed dogs and for the needle, and a top plate of much greater area disposed directly-,Jover and mounted on the aforesaid smaller base, said top plate having long slots for the leaf springs, the ends of said springs being offset downward at the ends of the slots, and portions of said springs being located between the base plate and the top plate.

7. A throat plate as defined in claim 4, in which there is a lower base having lthe dimension and outline of the regular throat plate in order to be lreceived in the opening for the regular throat plate, and having slots for the feed dogs and `for the needle, and a top plate of much greater area disposed directly over and mounted on the aforesaid smaller base, said top plate having long slots for the leaf springs, the ends of said springs being offset downward at the ends of the slots, and portions of said springs being located between the base plate and the top plate.

8. A throat plate as defined in claim 7, in which the wear strips secured -beneath the leaf springs are dimensioned to be matingly received in the relatively short slots of the base plate, and thereby serve to anchor the springs against longitudinal movement while permitting the desired vertical movement.

9. A throat plate as defined in claim 2, in which there is a lower base having the dimension and outline of the regular throat plate in order to be received in the opening for the regular throat plate, and having slots for the feed dogs and for the needle, and a top plate of much greater area disposed directly over and mounted on the aforesaid smaller base, said top plate having slots for the leaf springs, the ends of said springs being offset downward at the ends of the slots, portions of said springs being located Ibetween the base plate and the top plate, and means on said springs to anchor the same against lateral movement while affording the desired up and down flexing movement.

References Cited UNITED STATES PATENTS 445,468 1/1891 Hanna 112-260 XR 1,122,999 12/1914 Pettit 112--260 2,024,435 12/1935 Eames 112--260 2,911,929 11/1959 Caldwell 112--260 XR JORDAN FRANKLIN, Primary Examiner. HAMPTON H. HUNTER, Assistant Examiner. 

1. A THROAT PLATE FOR USE IN A SEWING MACHINE WHEN USING AN ATTACHMENT PROVIDING ITS OWN FEED AND WHICH THEREFORE REQUIRES DISABLING OF THE REGULAR FEED DOGS OF THE SEWING MACHINE, SAID THROAT PLATE COMPRISING MEANS DISPOSED ENTIRELY OVER AND RESTING ON THE SEWING MACHINE FEED DOGS WHICH MEANS ARE ARRANGED TO RISE AND FALL WITH 